如何使用 Spring Data JPA 对两列求和？

Question

我想在我的数据库项目上总结两列，我正在使用 Spring Boot - Java，但我不知道我应该做什么

在数据库中我有那些列
id、user、value_income、outcome_value、total 和 income_property

我想做的基本上是从 value_income 和 outcome_value 从数据库中检索数据并在后端汇总

我的用户存储库：

package com.saturnssolutions.TakeMoney.repositories;

import com.saturnssolutions.TakeMoney.models.UserModel;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.Query;

import java.math.BigDecimal;
import java.util.List;

public interface UserRepository extends JpaRepository<UserModel, Integer> {
    @Query("SELECT UserModel.id, (UserModel.valueIncome + UserModel.outcomeValue) as AddedValues FROM money")
    List<UserModel> findAllByTotal;
}

ps：我记得ps 收到错误

我的用户控制器：

package com.saturnssolutions.TakeMoney.controllers;

import com.saturnssolutions.TakeMoney.models.UserModel;
import com.saturnssolutions.TakeMoney.services.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.*;

import java.util.List;
import java.util.NoSuchElementException;
@RestController
@RequestMapping("/api/v1")
public class UserController {
    @Autowired
    UserService userService;

    @CrossOrigin
    @GetMapping("/users")
    public List<UserModel> listAllUsers() {
        return userService.listAllUsers();
    }

    @CrossOrigin
    @GetMapping("/users/{id}")
    public ResponseEntity<UserModel> users(@PathVariable Integer id) {
        try {
            UserModel user = userService.getUser(id);
            return new ResponseEntity<UserModel>(user, HttpStatus.OK);
        } catch (NoSuchElementException e) {
            return new ResponseEntity<UserModel>(HttpStatus.NOT_FOUND);
        }
    }
    @CrossOrigin
    @PostMapping("/users")
    public void users(@RequestBody UserModel user) {
        userService.saveUser(user);
    }
    @CrossOrigin
    @PutMapping("/users/{id}")
    public ResponseEntity<?> update(@RequestBody UserModel user, @PathVariable Integer id) {
        try {
            UserModel existUser = userService.getUser(id);
            user.setId(id);
            userService.saveUser(user);
            return new ResponseEntity<>(HttpStatus.OK);
        } catch (NoSuchElementException e) {
            return new ResponseEntity<>(HttpStatus.NOT_FOUND);
        }
    }
    @CrossOrigin
    @DeleteMapping("/users/{id}")
    public void delete(@PathVariable Integer id) {

        userService.deleteUser(id);
    }

    @CrossOrigin
    @GetMapping("/users/total")
    public Float getTotal(){
        return userService.getTotal();
    }
}

我的服务：

package com.saturnssolutions.TakeMoney.services;

import com.saturnssolutions.TakeMoney.models.UserModel;
import com.saturnssolutions.TakeMoney.repositories.UserRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import javax.transaction.Transactional;

import java.math.BigDecimal;
import java.util.List;

@Service
@Transactional
public class UserService {
    @Autowired
    private UserRepository userRepository;

    public List<UserModel> listAllUsers() {
        return userRepository.findAll();
    }

    public void saveUser(UserModel user) {
        userRepository.save(user);
    }

    public UserModel getUser (Integer id) {
        return userRepository.findById(id).get();
    }

    public void deleteUser (Integer id) {
        userRepository.deleteById(id);
    }

    public List<UserModel> getTotal() {
        return userRepository.findAllByTotal();
    }
}

和我的模型：

package com.saturnssolutions.TakeMoney.models;

import javax.persistence.*;
import java.math.BigDecimal;

@Entity
@Table(name = "money")
public class UserModel {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;

    private String user;
    private Float valueIncome;
    private Float outcomeValue;
    private Float total;
    private Boolean incomeProperty;

    public Boolean getIncomeProperty() {
        return incomeProperty;
    }

    public void setIncomeProperty(Boolean incomeProperty) {
        this.incomeProperty = incomeProperty;
    }

    public String getUser() {
        return user;
    }

    public void setUser(String user) {
        this.user = user;
    }

    public Float getValueIncome() {
        return valueIncome;
    }

    public void setValueIncome(Float valueIncome) {
        this.valueIncome = valueIncome;
    }

    public Float getOutcomeValue() {
        return outcomeValue;
    }

    public void setOutcomeValue(Float outcomeValue) {
        this.outcomeValue = outcomeValue;
    }

    public Float getTotal() {
        return total;
    }

    public Float setTotal(Float total) {
        this.total = total;
        return total;
    }

    public UserModel() {
    }

    public UserModel(Integer id, String user, Float valueIncome, Float outcomeValue, Float total) {
        this.id = id;
        this.user = user;
        this.valueIncome = valueIncome;
        this.outcomeValue = outcomeValue;
        this.total = total;
    }

    public Integer getId() {
        return id;
    }

    public Integer setId(Integer id) {
        return this.id = id;
    }

}

Answer 1

你的存储库的这个版本应该可以工作：

public interface UserRepository extends JpaRepository<UserModel, Integer> {
    @Query("SELECT id, valueIncome + outcomeValue AS AddedValues FROM money", nativeQuery=true)
    List<Object[]> findAllByTotal;
}

请注意，在 JPA 查询中引用 UserModel 将不起作用，因为 JPA 需要 table 名称。此外，不需要别名，因为您只是 select 针对单个 table/entity.

此外，您的查询必须作为本机查询执行，因为它 returns 计算列。您还可以仅使用 select 语句中的两个字段来定义自定义 POJO。使用前一个 List<Object[]> 选项，您的代码应该类似于：

List<Object[]> vals = userRepository.findAllByTotal();
for (Object[] row : vals) {
    int id = (Integer)row[0];
    double addedValues = (Double)row[1];
}

您可能需要尝试在上面的 for 循环中进行强制转换才能使其正常工作。

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